The NFL and the NFL Players Association have reached a tentative agreement on human growth hormone testing this season, according to a players' union memo.

The memo, which was sent to all NFL players and their representatives and obtained by The Baltimore Sun, follows an agreement on an HGH population study to determine baseline levels of HGH hormones.

Forty players, five randomly chosen from eight teams, would be randomly tested per week once HGH testing begins. All players would have to submit to a blood test for the population study prior to the launch of testing.

A first positive test would trigger a four-game suspension for violating the NFL performance-enhancing drug policy pending any potential appeal.

The NFL hasn't announced an agreement yet, but the players' union seems pretty clear-cut in its memo.

Here is the memo from the union outlining what's to follow:

1. What is the purpose of the NFLPA and NFL’s agreement to conduct a population study?

The purpose is to determine the decision limit that is accurate for the NFL player population. All human beings naturally produce human growth hormone. Thus, unlike a test for a foreign substance, in which detection of any level of the substance indicates ingestion of the substance, the reasoning behind the isoform HGH test is that a blood sample that generates a result above the decision limit indicates use of exogenous (not naturally produced by the body) HGH. In other words, if a person has a level above the decision limit, they must have used exogenous human growth hormone because no one can naturally produce a level above the decision limit. So, if a person has a result above the decision limit, that result constitutes a “positive” test result.

2.Why do the NFLPA and NFL have to conduct a population study to determine the decision limit that is appropriate for NFL players?

Since August 2011, when NFLPA began researching the isoform HGH test, which was created by the World Anti-Doping Agency (WADA) and is the only test for HGH on the market, we have been very concerned with the method that WADA used to determine the decision limit that it set. Then, in March 2013, the highest international court for Olympic sport cases determined that the WADA decision limit is, in fact, unreliable. Therefore, the NFLPA informed NFL that the only way to move forward with HGH testing as part of the Performance Enhancing Substances Policy is for the parties to jointly hire independent scientists to conduct a scientifically rigorous population study to determine the correct decision limit for NFL players.

3.What is required of me for the population study?

A. All players who participate in NFL training camps in 2013 must provide one blood serum sample (the same small vial used for blood drawn for a normal physical exam) that will be drawn at the facility by collectors who have been trained and licensed to draw blood, and;

B. At the time you provide the blood sample, you will provide the collector with the biometric information that the scientists need to calculate the decision limit: height, weight, age, and race/ethnicity.

C. Players will also provide their phone contact information, which will only be provided to Dr. Rogol, the independent doctor overseeing the study, so that he can contact a player if a test result indicates a possible serious medical issue about which he must notify the player.

4. What happens to my blood after it is drawn for the population study?

Your sample will be immediately sealed and labelled with a number that matches to your name in a computer database -- ONLY Dr. Rogol, the independent scientist managing the study, can access that database, and he will only do so if he needs to alert a player to a medical issue indicated by a test result. It will be shipped to either the UCLA Olympic Analytical Laboratory in Los Angeles or the Sport Medicine Research Laboratory in Salt Lake City. At the lab, the sample with be run through the isoform HGH test, and the data from the test will be provided to the independent scientists (they have no relationship with either the NFL or NFLPA other than this study) who have been jointly hired for the exclusive purpose of designing and conducting the population study. The labs are legally and contractually obligated to destroy ALL blood samples and provide verifiable certification of destruction to the NFLPA and NFL. Absolutely NO OTHER USE of the blood will be permitted. NFLPA will notify the membership of the destruction of the all samples after the laboratory notifies the NFLPA.

5.Will anyone know which sample belongs to me and what result my sample generated when run through the test at the laboratory?

Until the decision limit is established, only ONE person, Dr. Al Rogol, who is the independent doctor hired to oversee and conduct the population study, will have the ability to connect a sample number with a player name; he will ONLY do so if a result indicates that the sample donor may have a medical issue about which he must be alerted.

After the decision limit is established, if 5% or more of all player samples show test results above the decision limit, the information connecting those sample numbers with player names will be provided to the Medical Advisor for the Policy on Steroids and Related Substances, Dr. John Lombardo. He will inform those players that they are on “reasonable cause” testing through the end of the 2014-2015 season. If those players do not have another positive test, at the end of the 2014-2015 season, they will be removed from reasonable cause testing. If they do test positive again before the end of the 2014-2015 season, they will be disciplined at Step Two of the Policy, which is an 8 game suspension.

6.Will players be able to get a copy of their test result?

There are only two circumstances in which a player can obtain his test result:

A) Prior to determination of the decision limit, if a test result is extremely unusual and thus raises a medical issue concern, Dr. Rogol will connect a sample number with a player name and inform the player;

B) After the decision limit is determined, if the 5% threshold is met, those players who had positive population study samples will be informed by Dr. Lombardo that they are in reasonable cause testing through the end of the 2014-2015 season.

7. If a sample generates an extremely low result that indicates a medical issue, will he be able to obtain a therapeutic use exemption to treat the issue?

The doctor and scientists have informed us that an extremely low level of human growth hormone will not appear in an NFL player because the medical effect of that condition is so rare, and the physical impact is so extreme, that it would have severely impacted a player’s physical development as a child and adult. However, if there is some other medical issue that a very unusual result indicates, the player will be informed.

8. Will there be testing during the season after the population study sample is taken during training camp?

We have tentatively agreed (and will likely finalize soon, when a few other issues in Policy are settled) that each week during the season, a computer program will randomly select 5 men from 8 teams each week to provide blood. The blood will be tested immediately, then frozen. The test results will be stored in a computer, and once the decision limit is determined, the results will be compared with the decision limit.

If a player’s blood sample produced a result above the decision limit, that is a positive test, and that player will be disciplined at Step One of the Policy, which is a four game suspension. The player will have the right to appeal that discipline, and his blood will have been frozen and stored. NO OTHER USE will be made of the blood, and it will be destroyed within 60 days of his appeal.